As a movement for estimating the physical strength of a subject, an STS (sit-to-stand) movement is known which is also called a stand-up-from-a-chair movement. An STS movement is a movement that involves moving the center of gravity of the subject's body weight from a comparatively low support base face to a comparatively high position.
In Non-Patent Document 1 identified below, a summary is presented of the relationship among the moments at the hip, knee, and ankle in an STS movement, and it is reported that, irrespective of how the subject stands up in an STS movement, the sum of the moments at the hip and knee in healthy subjects exhibits a constant value (1.53 N·m/kg) and that there is almost no correlation between that sum and the moment at the ankle. It is also reported that, if the sum of the moments at the hip and knee in an STS movement is less than the above-mentioned constant value, a problem is suspected in the subject's ability to stand up, suggesting the necessity for an appropriate exercise therapy to prevent confinement to bed and to motivate to rehabilitation.